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| United States Patent |
6,072,173
|
|
Soshi
, et al.
|
June 6, 2000
|
Animal body detecting system utilizing electromagnetic waves
Abstract
An animal body detecting system adapted to be mounted on a vehicle is
capable of simply and accurately detecting whether or not an animal
exists, i.e. for detecting a distance to an object in front of the vehicle
and for discriminating whether or not the object is an animal at the same
time, by utilizing electromagnetic waves. The system is comprised of
transceiver devices for emitting a radio wave of a first frequency of 10
GHz and that of a second frequency of 60 GHz whose frequency is higher
than the first frequency in the same direction and for receiving reflected
waves; and discriminating devices for generating material detection data
indicative of whether or not a combination, i.e. a ratio or a product, of
receiving levels of the reflected waves of the respective frequencies is a
combination of the case when the reflecting object is an animal body. It
further comprises a detector for detecting a distance to the reflecting
object based on the emitted waves and the received reflected waves. The
system utilizes the discrimination result of whether or not the object is
an animal and the measured distance thereto when traveling at night, in
controlling the distance between vehicles and in controlling a vehicle
speed.
| Inventors:
|
Soshi; Kunihiko (Ushiku, JP);
Nakane; Takeshi (Okazaki, JP)
|
| Assignee:
|
Aisin Seiki Kabushiki Kaisha (Kariya, JP)
|
| Appl. No.:
|
081616 |
| Filed:
|
May 20, 1998 |
Foreign Application Priority Data
| Current U.S. Class: |
250/221; 340/435; 340/903 |
| Intern'l Class: |
G08G 001/16 |
| Field of Search: |
250/221,222.1
340/435,436,903
342/70,85
|
References Cited
U.S. Patent Documents
| 5227784 | Jul., 1993 | Masamori et al. | 340/436.
|
| 5777563 | Jul., 1998 | Minissale et al. | 340/435.
|
| 5936549 | Aug., 1999 | Tsuchiya | 340/903.
|
Primary Examiner: Allen; Stephone
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas, PLLC
Claims
What is claimed is:
1. An animal body detecting system utilizing electromagnetic waves,
comprising:
transceiver means for emitting the electromagnetic wave of a first
frequency and that of a second frequency whose frequency is higher than
the first frequency substantially in the same direction and for receiving
reflected waves from the front in the electromagnetic wave emitting
direction; and
discriminating means for generating information indicative of whether or
not a combination of receiving levels of received reflected waves of the
respective frequencies is a combination of the case when the reflecting
object is an animal body.
2. An animal body detecting system utilizing electromagnetic waves,
comprising:
transceiver means for emitting the electromagnetic wave of a first
frequency and that of a second frequency whose frequency is higher than
the first frequency substantially in the same direction and for receiving
reflected waves from the front in the electromagnetic wave emitting
direction; and
discriminating means for generating information indicative of whether or
not a ratio of receiving levels of received reflected waves of the
respective frequencies is a ratio of the case when the reflecting object
is an animal body.
3. The animal body detecting system utilizing electromagnetic waves
according to claim 2, further comprising means for detecting a distance
between said transceiver means and the reflecting object based on the
emitted wave of one frequency and the received reflected wave.
4. The animal body detecting system utilizing electromagnetic waves
according to claim 3, wherein said one frequency is the first frequency.
5. An animal body detecting system utilizing electromagnetic waves,
comprising:
first transceiver means for emitting the electromagnetic wave of a first
frequency and for receiving reflected waves from the front in the
electromagnetic wave emitting direction;
second transceiver means for emitting the electromagnetic wave of a second
frequency whose frequency is higher than the first frequency in the
direction in which the electromagnetic wave of the first frequency is
emitted and for receiving the reflected wave from the front in the
electromagnetic wave emitting direction;
means for detecting a distance between said transceiver means and the
reflecting object based on the emitted wave of one frequency and the
reflected received wave;
discriminating means for generating information indicative of whether or
not a ratio of receiving levels of received reflected waves of the
respective frequencies is a ratio of the case when the reflecting object
is an animal body; and
means for informing of said information and said distance.
6. The animal body detecting system utilizing electromagnetic waves
according to claim 5, wherein said one frequency is the first frequency.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for detecting whether an object
exists or not by utilizing electromagnetic waves and more particularly, to
a system for discriminating whether or not the detected object is an
animal, including a human. This system may be used as a vehicular front
monitoring system for measuring a distance to an object existing ahead of
the vehicle.
2. Description of Related Art
Hitherto, as a monitoring system of this sort, there have been systems of
shooting a scene ahead of a vehicle by a camera and processing its image
to discriminate an object existing ahead of the vehicle and of emitting
laser beams or electromagnetic waves such as radio waves ahead of the
vehicle to detect the wave reflected by an object existing ahead of the
vehicle. Their ordinary purpose is to detect a distance to a preceding
vehicle going ahead of the vehicle or an obstacle existing ahead of the
vehicle. They can detect an object existing ahead of the lane of the
vehicle and measure a distance to the object accurately on motor ways such
as highways where pedestrians and bicycles are prohibited and which are
standardized.
However, on ordinary roads, there are pedestrians and bicyclers who are
coming and going on or near the road surface where vehicles travel or who
try to cross the road. Further, even on a motor way, there is a case when
a car stops at the road side to pick up or discharge passengers or when
construction workers work there. Animals also often prowl on mountainous
roads. It is hard to pedestrians, animals and bicyclers traveling adjacent
roads especially in the night time. Hereinafter, man and other animals
will be expressed simply as animals.
There has also been proposed a front monitoring system for sensing an
animal by using an infrared camera. However, because the infrared camera
senses infrared rays emitted from warm objects, it also reacts to road
lamps, a head light of a vehicle running in the opposite direction, a
muffler and tires of a vehicle running ahead. Then, highly advanced shaped
recognition technology or motion recognition technology must be combined
with it in order to discriminate animals singularly, so that the
monitoring system becomes costly. Furthermore, its discriminating accuracy
is relatively low.
Although animals reflect radio waves whose wavelength is short and it is
possible to detect reflected waves from animals, it is difficult to detect
animals, e.g., a pedestrian, singularly because the intensity of the
reflected wave from a metal having a high electrical conductivity is
greater.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to detect
whether an animal exists or not by utilizing electromagnetic waves. A
second object is to detect a distance to a front object and to
discriminate whether or not the front object is an animal at the same time
and a third object is to realize the determination as to whether or not it
is an animal by a relatively simple technology.
In order to achieve the above-mentioned objects, the present invention
system is constructed as follows.
(1) An inventive animal body detecting system utilizing electromagnetic
wave comprises transceiver means (11, 12, 14 and 15) for emitting the
electromagnetic wave of a first frequency (10 GHz) and that of a second
frequency (60 GHz) whose frequency is higher than the first frequency
substantially in the same direction and for receiving reflected waves from
the front in the electromagnetic wave emitting direction; and
discriminating means (16 and ECU 1) for generating information indicative
of whether or not a combination of receiving levels of the received
reflected waves of the respective frequencies is a combination of the case
when the reflecting object is ax animal body.
It is noted that reference numerals of components or matters corresponding
to those shown in the drawings and described later in a preferred
embodiment are added in parentheses for reference so that the invention
can be readily understood.
Although animals reflect radio waves of short wavelength and it is possible
to detect the wave reflected from the animals, its reflectance differs
depending on its wavelength (frequency) and on a physical property
(electrical conductivity) of the object to which the radio wave hits.
Table 1 shows receiving rates [(receiving intensity/transmitting
intensity).times.100%] obtained by emitting radio waves to several kinds
of materials and by receiving the waves reflected from the materials in
correspondence to frequencies of the emitted radio waves. Table 2 shows
approximate sizes of the various materials shown in Table 1 and a distance
between the materials and an antenna when the data in Table 1 is obtained.
TABLE 1
__________________________________________________________________________
RECEIVING RATIO AND PRODUCT AND
INTENSITY/
DETERMINATION BASED ON THAT
DETERMINATION BASED ON THAT
TRANSMITTING DETERMINATION DETERMINATION
FRONT INTENSITY (%)
10 GHz/
THRESHOLD
1: ANIMAL
10 GHz/
THRESHOLD
1: ANIMAL
OBJECT 10 GHz
60 GHz
60 GHz
VALUE 2: OTHERS
60 GHz
VALUE 2:
__________________________________________________________________________
OTHERS
HAND 0.3940
0.2396
1.6444
1.4 1 0.094
0.04
1.0
1
TULIP 0.0394
0.0332
1.1872
1.4 0 0.001
0.04
1.0
0
PEAR 0.0243
0.0212
1.1471
1.4 0 0.001
0.04
1.0
0
PALM 0.0098
0.0101
0.9695
1.4 0 0.000
0.04
1.0
0
ORANGE 0.0201
0.0210
0.9575
1.4 0 0.000
0.04
1.0
0
RADISH 0.0579
0.1193
0.4853
1.4 0 0.007
0.04
1.0
0
PLATE 0.0368
0.1570
0.2345
1.4 0 0.006
0.04
1.0
0
(LUMBER)
IRON 1.4655
7.1200
0.2058
1.4 0 10.434
0.04
1.0
0
CONCRETE 0.0296
0.1713
0.1730
1.4 0 0.005
0.04
1.0
0
INFORMATION
A B C D E F G H
__________________________________________________________________________
TABLE 2
______________________________________
SIZE DISTANCE TO ANTENNA
______________________________________
HAND AREA: about 1300 mm.sup.2
500 mm
TULIP HEIGHT: about 280 mm
PEAR HEIGHT .times. WIDTH:
about 120 mm .times. 150 mm
PALM HEIGHT: about 350 mm
ORANGE HEIGHT .times. WIDTH:
about 100 mm .times. 120 mm
RADISH LENGTH .times. THICKNESS:
about 300 mm .times. 80 mm
PLATE 1000 mm.sup.2
(LUMBER)
IRON 1000 mm.sup.2
CONCRETE
1200 mm.sup.2
______________________________________
All of the plants have been measured by using the whole body without
cutting.
FIG. 5 shows the receiving rates of iron and hand within a range from 10 to
60 GHz by alternate chain lines, The left vertical axis thereof represents
values of tho receiving rates. The Figure also shows ratios of receiving
rates within the range (receiving rate when 10 GHz/receiving rate when
each frequency) by dotted lines. The right vertical axis represents values
of the ratio of receiving rates.
Numerical values in Information Item A on Table 1 are receiving rates when
the frequency of the radio wave is 10 GHz and those in Information Item B
are receiving rates when the frequency is 60 GHz. Numerical values in
Information Item c are the ratios of receiving rates (receiving rate when
10 GHz/receiving rate when 60 GHz).
Information Item D shows one exemplary threshold value for discriminating
only animals based on the ratio of receiving rates and Information Item E
shows binarized data when the ratio of receiving rates is binarized by the
threshold value. "1" in the binarized data indicates that the ratio of
receiving rates exceeds the threshold value, meaning that an object is a
hand (animal) in this case. "0" in the binarized data indicates that the
ratio of receiving rates is less than the threshold value, meaning that
the object is not a hand (animal) in this case.
Numerical values in Information Item F on Table 1 are products of receiving
rates (receiving rate when 10 GHz.times.receiving rate when 60 GHz). Those
in Information Item G are pairs of threshold values for discriminating
only animals based on the product of receiving rates and those in
Information Item H are binarized data showing that the product of
receiving rates is within the range of the pairs of the threshold values
(animal) or is out of the range (not animal). "1" in this binarized data
indicates that the product of receiving rates is within the range between
the pair of threshold values, meaning that an object is a hand (animal) in
this case. "0" in the binarized data indicates that the product of
receiving rates is out of the range, meaning that the object is not a hand
(animal) in this case.
When the transmitting intensity of the radio wave of 10 GHz is denoted by
E.sub.T1O and the reflected wave receiving intensity by E.sub.R10 and the
transmitting intensity of the radio wave of 60 GHz is denoted by E.sub.T60
and the reflected wave receiving intensity by E.sub.R60 in the example
described above, their receiving rates are expressed as follows:
Receiving Rate of Radio Wave of 10 GHZ=(E.sub.R10
/E.sub.T10).times.100(%)(1)
Receiving Rate of Radio Wave of 60 GHZ=(E.sub.R10
/E.sub.T10).times.100(%)(2)
The ratio of their receiving rates are then expressed as follows:
Ratio of Receiving Rates of Radio waves of Both Frequencies=(E.sub.R10
/E.sub.T10)/(E.sub.R60 /E.sub.T60)
=(E.sub.R10 /E.sub.R60)/(E.sub.T60 /E.sub.T10) (3)
The transmitting intensities E.sub.T10 and E.sub.T60 of both radio waves
are constant values (fixed values) defined by transmitters, so that they
are defined as a constant value (constant) also here, like:
Kr=(E.sub.T60 /E.sub.T10) (4)
Then, the ratio of receiving rates of the radio waves of both frequencies
turns out as follows:
Ratio of Receiving Rates=Kr.multidot.(E.sub.R10 /E.sub.R60)(5)
Accordingly, the ratio of receiving rates can be found immediately from a
ratio of receiving levels (E.sub.R10 /E.sub.R60) of both frequencies. In
other words, when the threshold value in Information Item D is changed to
what (threshold value 1.4/Kr in Table 1) accommodates to the ratio of
receiving levels (E.sub.R10 /E.sub.R60), it becomes possible to
discriminate whether or not the object reflecting the radio waves is an
animal by comparing the ratio of receiving levels (E.sub.R10 /E.sub.R60)
with the threshold value accommodating to the ratio of receiving levels.
That is, it is possible to discriminate whether or not the object is an
animal based on the combination of the receiving levels of both
frequencies.
Similarly, a product of their receiving rates is expressed as follows:
Product of Receiving Rates of Radio Waves of Both Frequencies=(E.sub.R10
/E.sub.T10)/(E.sub.R60 /E.sub.T60) (6)
=(E.sub.R10 /E.sub.R60)/(E.sub.T10 /E.sub.T60) (7)
The transmitting intensities E.sub.T10 and E.sub.T60 of both radio waves
are constant values (fixed values) which are defined normally by
transmitters, so that they are set as a constant value (constant) also
here, like:
K.sub.T =1/(E.sub.T10 .times.E.sub.T60) (8)
Then, the product of receiving rates turns out as follows:
Product of Receiving Rates of Radio Waves of Both
Frequencies=K.sub.T .multidot.(E.sub.R10 .times.E.sub.R60) (9)
Accordingly, the product of receiving rates can be found immediately from a
product of receiving levels E.sub.R10 .times.E.sub.R60 of both
frequencies. In other words, when the threshold value in the Information
Item F is changed to what (threshold values 0.04/K.sub.T and 1.0/K.sub.T
in Table 1) accommodate to the product of receiving levels (E.sub.R10
.times.E.sub.R60), it is possible to discriminate whether or not the
object reflecting the radio waves is an animal by comparing the product of
receiving levels (E.sub.R10 .times.E.sub.R60) with the threshold values
accommodating to the product of receiving levels. That is, it is possible
to discriminate whether or not the object is an animal based on the
combination of the receiving levels of both frequencies.
As described above, the present invention allows the object to be
discriminated whether or not it is an animal relatively simply and
accurately because it is discriminated based on the combination of the
receiving levels of the different frequencies.
However, when the distance to the reflecting object is not constant, the
receiving levels E.sub.R10 and E.sub.R60 vary depending on the distance.
FIG. 6 shows a relationship between the distance and the receiving rates
of the hand (described as a human body in FIG. 6) and iron shown in Table
2. It is noted that the graph shown in FIG. 6 represents values calculated
by using the radar equation based on the receiving rates (receiving
intensity/transmitting intensity when the distance is 500 mm) as shown in
Table 1.
Because the product of receiving levels (E.sub.R10 .times.E.sub.R60) varies
depending on the distance to the reflecting object, the object may be
discriminated based on the product of receiving levels whether it is an
animal or not only when the object is substantially within a constant
distance. Alternatively, it is necessary to measure the distance to the
object to correct the threshold value or to correct the receiving level
corresponding to the distance. With respect to the discrimination mode
based on the product of receiving levels, a monitoring distance of a
static monitoring system for discriminating whether or not an object
exists at a specific location (fixed area) (whether the object enters or
leaves) and whether or not it is an animal, for example, is limited
(because it is substantially fixed), so that the threshold value or
receiving levels need not be corrected substantially corresponding to the
distance, allowing the object to be discriminated relatively simply and
accurately.
It is possible to discriminate whether or not the object is an animal
similarly also by the static monitoring system of this sort based on added
values or subtracted values of the receiving rates or the receiving levels
of both frequencies or by way of mapping for determining that the
combination of the receiving rates or the receiving levels of both
frequencies belongs to which realm section (animal/metal/others
parameterized by them. These discrimination modes are applicable to the
mode in which the distance to the object is not constant or not defined
(in detecting an animal body existing ahead of a running vehicle for
example) by measuring the distance to the object to correct the threshold
value or to correct the receiving levels corresponding to the distance
before the discrimination.
When the object is discriminated whether or not it is an animal based on
the ratio of receiving levels (E.sub.R10 /E.sub.R60), although each of the
receiving intensities E.sub.R10 and E.sub.R60 varies depending on the
distance to the object, each of the receiving intensities E.sub.R10 and
E.sub.R10 change substantially in the same rate in the same direction with
respect to the changes of the distance to the object. Accordingly, the
change of their ratio, i.e. the change of the ratio of receiving levels
(E.sub.R10 /E.sub.R60) is small and the object may be discriminated
whether or not it is an animal simply and at high precision even when the
distance to the object is not constant or not defined.
(2) According to another mode of the invention, an animal body detecting
system utilizing electromagnetic waves comprises transceiver means (11,
12, 14 and 15) for emitting the electromagnetic wave of a first frequency
(10 GHz) and that of a second frequency (60 GHz) whose frequency is higher
than the first frequency substantially in the same director and for
receiving reflected waves from the front in the electromagnetic wave
emitting direction; and discriminating means (16 and ECU 1) for generating
information indicative of whether or not a ratio of receiving levels of
the received reflected waves of the respective frequencies is a ratio of
the case when the reflecting object is an animal body.
This is a mode of using the above-mentioned ratio of receiving levels
(E.sub.R10 /E.sub.R60) as a discriminatory parameter and allows the object
to be discriminated whether or not it is an animal simply and at high
precision even when the distance to the object (reflecting object) is not
constant or not defined.
(3) The inventive animal body detecting system utilizing electromagnetic
waves of the above-mentioned mode (2) further comprising means (12 and 13)
for detecting the distance between the transceiver means (11, 12, 14 and
15) and the reflecting object based on the emitted wave of one frequency
(10 GHz) and the received reflected wave. It allows the distance to the
front object to be detected and the object to be discriminated whether or
not it is an animal substantially in the same time.
(4) An inventive animal body detecting system utilizing electromagnetic
waves comprises first transceiver means (11 and 12) for emitting the
electromagnetic wave of a first frequency (10 GHz) and for receiving
reflected waves from the front in the electromagnetic wave emitting
direction; second transceiver means (14 and 15) for emitting the
electromagnetic wave of a second frequency (60 GHz) whose frequency is
higher than the first frequency in the direction in which the
electromagnetic wave of the first frequency (10 GHz) is emitted and for
receiving the reflected wave from the front in the electromagnetic wave
emitting direction; means (12 and 13) for detecting a distance between the
transceiver means (11 and 12) and the reflecting object based on the
emitted wave of one frequency (10 GHz) and the received reflected wave;
discriminating means (16 and ECU 1) for generating information indicative
of whether or not a ratio of receiving levels of received reflected waves
of the respective frequencies is a ratio of the case when the reflecting
object is an animal body; and means (ECU 2 and 4) for disclosing the
information and the distance.
It allows the distance to the reflecting object to be detected and the
reflecting object to be discriminated whether or not it is an animal at
the same time and allows them to be disclosed at the same time. This is a
mode of using the above-mentioned ratio of receiving levels (E.sub.R10
/E.sub.R60) as a discriminatory parameter and allows the object to be
discriminated whether or not it is an animal simply and at high precision
even when the distance to the object is not constant or not defined. This
may be suitably used in the vehicle front monitoring system described
above.
(5) The invention is also characterized in that in the animal body
detecting system utilizing electromagnetic wave of the mode (3) or (4),
the one frequency is the first frequency 10 GHz.
Because the receiving rate of a hand (animal) is relatively low and the
receiving rate drops, though slightly, as the frequency increases as shown
in FIG. 5, the low frequency radio wave is preferable to increase the
detecting accuracy of the hand (animal) because its receiving rate is
higher. Accordingly, the first frequency (10 GHz), i.e. the lower
frequency, is set as the frequency for detecting the distance in this mode
(5). It is noted that with respect to iron (metal: high electrical
conductor), although its receiving rate of the high frequency radio wave
is high, allowing the detecting accuracy to be high, its receiving rate of
the first frequency (10 GHz), i.e. the lower frequency, is still higher
than the receiving rate of hand (animal), so that the detecting accuracy
of iron (e.g. a vehicle) is not hampered so much at a short distance.
The above and other objects, features and advantages of the present
invention will be more apparent and more readily appreciated from the
following detailed description of preferred exemplary embodiment of the
present invention, taken in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram showing a structure of vehicle front monitoring
system comprising a front object monitoring unit according to one
embodiment of the present invention.
FIG. 2a is a side view of the front object monitoring unit shown in FIG. 1
and
FIG. 2b is a front view of the front object monitoring unit shown in FIG. 1
when seen from the front side of the vehicle.
FIG. 3 is a block diagram showing a first transceiver and a second
transceiver shown in FIG. 2.
FIG. 4 is a flow chart showing an outline of an operation of an ECU shown
in FIG. 3.
FIG. 5 is a graph showing receiving rates and a ratio of receiving rates
when a radio wave is emitted to two kinds of objects (iron and hand).
FIG. 6 is a graph showing a relationship between distance and receiving
rates of the hand (described as a human body in FIG. 6) and the iron shown
in Table 2.
FIG. 7 is a flow chart showing a part of an outline of an operation of the
CPU shown in FIG. 1; and
FIG. 8 is a flow chart showing a remaining part of the outline of the
operation of the CPU shown in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows one embodiment of the present invention. This embodiment is
realized in a vehicular front monitoring system which is provided in a
vehicle having an internal combustion engine. A front object monitoring
unit 10 utilizing electromagnetic waves is connected to an input/output
interface (input signal processing circuit and output signal processing
circuit) 2 of a host electronic control unit ECU 2. A CPU 3 issues a
measure command to the front object monitoring unit 10 via the
input/output interface 2.
FIGS. 2a and 2b schematically show the structure of the front object
monitoring unit 10. The front object monitoring unit 10 comprises a first
antenna 11, opening to the front of the vehicle, for both emitting and
receiving the radio wave of 10 GHz (first frequency) and a first
transceiver 12 connected thereto, a second antenna 14, similarly opening
to the front of the vehicle, for both emitting and receiving the radio
wave of 60 MHz (second frequency) and a second transceiver 15 connected
thereto, a level detector 16 for detecting a receiving level of each
frequency and generating digital data indicative of that, a pulse count
type wave analyzer 13 for measuring a frequency of a beat signal output by
the first transceiver 12 and for converting it into distance information
and an electronic control unit ECU 1 for giving FM pulses (frequency
modulated synchronizing pulses) to the first transceiver 12 and for
reading the output (level data) of the level detector 16 as well as the
output (distance data) of the wave analyzer 13. The ECU 1 is connected to
the input/output interface 2.
Similarly to the host ECU 2, the ECU 1 comprises mainly a CPU and an
input/output interface (not shown). When the host ECU 2 issues a
monitoring command (monitor ON) to the ECU 1, it turns on the transceivers
12 and 15, the level detector 16 and the wave analyzer 13, issues FM
pulses to the first transceiver 12 at constant cycle, reads the level data
(output by the level detector 16) and the distance data (output by the
wave analyzer 13) substantially at constant cycle and calculates the ratio
of receiving rates every time in reading them:
Ratio of Receiving Rates=Kr.multidot.(E.sub.R10 /E.sub.R60)(5)
where, Kr is a coefficient (fixed value) defined based on output powers
(designed values) of transmitters of the transceivers 12 and 15, E.sub.R10
is a receiving level of the reflected wave of the first frequency of 10
GHz, i.e. the value indicated by the output data of the level detector 16,
and ER.sub.60 is a receiving level of the reflected wave of the second
frequency of 60 GHz, i.e. a value indicated by the output data of the
level detector 16. Then, the ECU 1 outputs material detection data and
distance data read from the wave analyzer 13 to the host ECU 2 by
indicating the material detection data as "1" representing an "animal"
when the calculated ratio of receiving rates exceeds a threshold value
(value corresponding to 1.4 in Information Item D in Table 1) and as "0"
representing an "object other than animals" when the ratio is less than
the threshold value.
FIG. 3 shows an outline of the structure of the first and second
transceivers 12 and 15. According to the present embodiment, the first
transceiver 12 and the first antenna 11 compose, together with the wave
analyzer 13, an FM-CW radar for transmitting/receiving the radio wave of
10 GHz to detect a beat frequency caused by phase shift of the transmitted
radio wave and the received reflected radio wave to calculate a distance
to a front reflecting object.
A triangular wave generator 21 generates triangular waves synchronized with
the FM pulses given by (the CPU within) the ECU 1 and supplies them to a
voltage controlled variable frequency oscillator 22. While a center
frequency of the signal generated by the oscillator 22 is 10 GHz, the
frequency of the output signal of the oscillator 22 fluctuates within a
range of 9.5 to 10.5 GHZ. This oscillating signal is applied to the horn
antenna 11 via an isolator 23, a directional coupler 24, an isolator 25
and a directional coupler 26. Thereby, the frequency modulated radio wave
of 9.5 to 10.5 GHz is emitted ahead of the vehicle.
When the ECU 11 receives part of the radio wave reflected from the front
object, the received signal reaches a mixer 30 via the directional coupler
26, an isolator 27 and directional coupler 28. Meanwhile, a part of the
transmitted signal is given to the mixer 30 via the directional coupler 24
and an isolator 29. The mixer 30 mixes the transmitted signal and the
received signal to generate a signal of a beat frequency and gives it to
the wave analyzer 13.
The wave analyzer 13 of the present embodiment measures the beat frequency
by way of pulse count and outputs it by converting it into distance data
(updates and sets it at an output latch). It is noted that the wave
analyzer 13 may be what analyzes waveform components by fast Fourier
transformation to calculate a distance to and a relative speed of each
reflecting object which has brought about each component or may be
comprised of a filtering system.
Part of the received signal is supplied to the level detector 16 via the
directional coupler 28 and the level detector 16 calculates the receiving
level E.sub.R10 and updates and sets data indicative of that at an output
latch destined for the first frequency.
The second transceiver 15 supplies the signal of 60 GHz generated by the
oscillator 32 to the horn antenna 14 via an isolator 33 and a directional
coupler 36. Thus, the radio wave of 60 GHz is emitted ahead of the
vehicle. When part of the radio wave reflected from the front object is
received by the antenna 14, the received signal is supplied to the level
detector 16 via the directional coupler 36 and the level detector 16
calculates a receiving level E.sub.R60 and updates and sets data
indicative of that at an output latch destined for the second frequency.
Referring again to FIG. 1, a control/display board 4 for giving operation
commands and setting conditions to the CPU 3 is connected to the
input/output interface 2. The board 4 is provided with switches for
commanding front monitoring, control on distance between cars and control
on constant speed, an indicator lamp, a two-dimensional display and a
buzzer. The CPU 3 reads the control or status of the switches via the
input-output interface 2 and corresponding to that, turns the indicator
lamp on/off and implements "Front Monitoring", "Control on Distance
between Cars" and "Constant Speed Control" as described later.
Car speed synchronization pulses, each of which is generated per a
predetermined small angle of a rotating axle, are supplied to the CPU 3
via the input/output interface 2. Then, the CPU 3 calculates the car speed
by counting the pulse cycles of the car speed synchronization pulses.
Further, a steering angle sensor 5 generates an analog signal indicative
of a rotational angle of a steering wheel not shown and supplies it to the
CPU 3. In the "Control on Distance between Cars" and "Constant Speed
Control" described later, the CPU issues a signal instructing
acceleration, hold, deceleration or cancel to a throttle controller 6.
Corresponding to that signal, the throttle controller 6 controls an
actuator driver 7. The driver 7 drives a throttle actuator 8 coupled to a
throttle valve (not shown) of the engine of the vehicle. For instance,
when the CPU 3 instructs Acceleration, the throttle valve is driven and
opened via the throttle controller 6, the driver 7 and the throttle
actuator 8, an opening of the throttle valve is held as it is when the CPU
3 instructs Hold or the throttle valve is closed when the CPU 3 instructs
Deceleration. When the CPU 3 instructs Cancel, a clutch between the
throttle actuator 8 and the throttle valve is released and the throttle
valve automatically returns to an idling position by return force of a
return spring. It is the time when a driver of the vehicle releases an
accelerator pedal. When the driver steps on the accelerator pedal, the
throttle valve opens accordingly.
FIG. 4 shows a control operation of (the CPU within) the ECU 1 of the front
object monitoring unit 10. When the ECU 1 is turned on, it clears an
internal register, a counter and the like and sets a signal level at an
input/output port to the input/output interface within the ECU 1 to that
of the stand by state in Steps 1 and 2.
Next, the ECU 1 waits until when the host ECU 2 issue the measure command
(command signal "1") in Step 3. It is noted that the host ECU 2 issues the
measure command "1" to the ECU 1 when a head light switch of the vehicle
is turned on or when "Front Monitoring", "Control on Distance between
Cars" or "Constant Speed Control" is specified by the switch on the
control board 4 and issues a measure cancel command "0" to the ECU 1 when
the headlight switch is turned off and all of the "Front Monitoring",
"Control on Distance between Cars" or "Constant Speed Control" are
canceled.
When the host ECU 2 issues the measure command "1" to the ECU 1, the ECU 1
turns on the transceivers 12 and 15, the level detector 16 and the wave
analyzer 13 and starts to output the FM pulses of constant cycle to the
triangular wave generator 21 and the wave analyzer 13 in Step 5. Then, the
ECU 1 starts a timer Ts of Ts time interval in Step 6 and writes "1"
(indicative of on-measurement" to a register (one domain of an internal
memory in the CPU) MF in Step 7. Then, it waits until the time of the
timer Ts is over in Steps 7, 3, 4 and 8 and when the time is over, reads
output data (distance data) of the wave analyzer 13 and output data (level
data E.sub.R10 and ER.sub.60) of the level detector 16 in Step 9.
Next, it calculates the ratio of receiving rates.
Ratio of Receiving Rates=Kr.multidot.(E.sub.R10 /E.sub.R60)(5)
Kr is a coefficient (fixed value) defined based on the output power
(designed value) of the transmitters of the transceivers 12 and 15,
E.sub.R10 is a receiving level of the reflected wave of the first
frequency of 10 GHz, i.e. a value indicated by the output data of the
level detector 16, and E.sub.R60 is a receiving level of the reflected
wave of the second frequency of 60 GHz, i.e. a value indicated by the
output data of the level detector 16 as described before. Then, the ECU 1
outputs material detection data by indicating it as "1" indicating
"animal" when the calculated ratio of receiving rates exceeds a threshold
value TH (value corresponding to 1.4 in Information Item D in Table 1) and
as "0" indicating "object other than animals" when the ratio is less than
the threshold value TH in Step 10.
Next, the ECU 1 outputs this material detection data and the distance data
read from the wave analyzer 13 to the host ECU 2 (updates and sets at the
output latch to the host ECU 2) in Step 11. Then it restarts the timer Ts
in Step 12 and waits until the time of the timer Ts is over. Because the
above-mentioned Steps 9 and 10 are repeated when the measure command is
issued, the output data to the host ECU 2 is updated to the latest
detected value with the cycle of Ts.
When the measure cancel command is issued, the ECU 1 recognized it at Step
3. The ECU 1 then stops to output the FM pulses, shuts off the power to
the transceivers 12 and 15, the level detector 16 and the wave analyzer 13
in Step 13, clears the register MF in Step 14 and waits the measure
command to come in Step 3.
FIGS. 7 and 8 show a control operation of the CPU 3 of the host ECU 2 shown
in FIG. 1. Referring first to FIG. 7, when the CPU 3 is turned on, it
clears the internal register, the counter and the like and sets the signal
level of the input/output port to the input/output interface 2 to that in
the standby state in Steps 21 and 22. Next, the CPU 3 starts a timer Tm of
time interval of Tm in Step 23.
Then it reads the status of the head light switch and command switches on
the control board. When the head light switch and all of the command
switches are off, the CPU 3 waits until the head light switch or any one
of the command switches is turned on. When the switch is turned on, the
CPU 3 issues the measure command ("1") to the ECU 1, reads an angle signal
of the steering angle sensor 5 by converting from analog to digital and
reads the output data (distance data and material detection data) of the
ECU 1 in Step 24. It is noted that when the "Control on Constant Speed"
command switch is turned on from off, the CPU 3 reads a car speed at that
time to a target car speed register.
The CPU 3 checks the material detection data at first and when it turns out
to be "1" (detecting an animal), the CPU 3 sets to continuously energize
the buzzer on the control/display board 4 in Step 26. Thus, the buzzer
continuously sounds. Next, the CPU 3 displays the material (here
"pedestrian") indicated by the material detection date and a value
indicated by the distance data on the two-dimensional display on the
control/display board 4 in Step 27. Thus, a display "Pedestrian, at xxx m
Ahead" is made. Next, the CPU 3 cancels "Control on Distance Between Cars"
and "Control on Constant Speed" in Step 28. That is, it cancels the
automatic drive of the throttle valve. Therefore, the throttle valve
returns to the idling position when the accelerator pedal is not pressed.
After finishing the above-mentioned processes, the CPU 3 waits until the
time of the timer Tm is over.
When the material detection data is "0" (indicative of that it is not an
animal) in Step 25, the CPU 3 decides a front monitoring effective range
based on the steering angle data (data of the angle signal of the steering
angle sensor 5 converted from analog to digital) and the car speed read in
Step 24 in Step 29. That is, the effective range is defined such that the
larger the steering angle or the slower the car speed is, the shorter the
distance thereof in front of the vehicle becomes and the smaller the
steering angle or the faster the car speed is, the longer the distance
thereof in front of the vehicle becomes.
Next, the CPU 3 checks whether or not the distance data read in Step 24 is
within the effective range thus defined in Step 30. When it is out of the
effective range, there is no object within the effective range ahead of
the vehicle, so that the CPU 3 turns off the buzzer (there is a case when
it is not turned on) in Step 36 and displays on the two-dimensional
display that "No Object Ahead" in Step 37.
When the distance data is within the effective range, the CPU 3
discriminates whether the object corresponding to the distance data is a
preceding car or an obstacle in Step 31. Here, the CPU 3 calculates a
relative speed of the detected object with respect to own vehicle from
several past distance data and the distance data of this time and compares
this relative speed with the car speed of own vehicle to discriminate
whether the detected object is moving or is at a standstill. Then, the CPU
3 determines it as a preceding car when it is moving and as an obstacle
when it is at a standstill. Then, determining it to be a preceding car,
the CPU 3 turns off the buzzer in Step 36 and updates the display on the
two-dimensional display as "Preceding Car, at xxx m Ahead" in Step 37. xxx
m is a value represented by the distance data read this time in Step 24.
When it is determined to be an obstacle, the CPU 3 sets to buzz the buzzer
intermittently in Step 33, updates the display on the two-dimensional
display as "Obstacle, at xxx m Ahead" in Step 34 and cancels "Control on
Distance Between Cars" and "Control on Constant Speed Control" in Step 35.
Then, the throttle valve returns to the idling position when the
accelerator pedal is not pressed. After finishing the above-mentioned
processes, the CPU 3 waits until when the time of the timer Tm is over in
Step 42.
Referring now to FIG. 8, when the front detected object is determined to be
a preceding car and the display is updated in Steps 36 and 37 as described
above, the CPU 3 checks in Steps 38 and 40 whether "Control on Distance
Between Cars" or "Control on Constant Speed" is specified based on the
status data of the command switches read in Step 24. When "Control on
Distance Between Cars" is being specified, the CPU 3 executes "Control on
Distance Between Cars" in Step 39 and when "Control on Constant Speed" is
being specified, executes "Control on Constant Speed" in Step 41. When
neither of them is specified, the CPU 3 waits until the time of the timer
Tm is over in Step 42.
In "Control on Distance Between Cars" in Step 39, the CPU 3 reads a target
distance corresponding to the steering angle and the car speed from a data
table (one domain of the memory) to calculate a deviation of the measured
distance with respect to the target distance. When the deviation deviates
to the short distance side from an allowable range, the CPU 3 issues the
deceleration command to the throttle controller 6 when the deviation
deviates to the short distance side from an allowable range, issues the
acceleration command to the throttle controller 6 when the deviation
deviates to the long distance side from the allowable range and issues the
hold command to the throttle controller 6 when the distance is within the
allowable range.
When the car speed control command switch on the control/display board 4 is
turned on, the CPU 3 writes the car speed at the time to the target car
speed register. Then in "Control on Constant Speed" in Step 39, the CPU 3
calculates a deviation of the present car speed with respect to the target
car speed in the target car speed register. The CPU 3 issues the
deceleration command to the throttle controller 6 when the deviation
deviates to the high speed side from an allowable range, issues the
acceleration command to the throttle controller 6 when the deviation
deviates to the low speed side and issues the hold command to the throttle
controller 6 when it is within the allowable range.
After going through the above-mentioned processes, the CPU 3 waits until
the time of the timer Tm is over in Step 42. Then when the time is over,
it starts the timer Tm in Step 23 to implement the "Read Information" step
in Step 24. Thus the CPU 3 repeats the "Read Information" step in Step 24
and the processes of Steps 25 through 42 described above with the cycle of
Tm. It is noted that after detecting that the head light switch and all of
the command switches are off in "Read Information" in Step 24, the CPU 3
issues the measure cancel command ("0") to the ECU 1. Further, when the
command switch is turned off (canceled) during "Control on Distance
Between Cars" or "Control on Constant Speed", the CPU 3 then cancels the
control. Thereby the throttle valve returns to the idling position when
the accelerator pedal is not pressed.
The measure command ("1") is issued to the ECU 1 by the operation of the
CPU 3 of the host ECU 2 described above when the head light switch is ON
(supposed to be the night time) or when the switch of the front monitoring
command, the switch of the car distance control command or the switch of
the constant speed control command is ON. Then, the host ECU 2 measures
the distance to the front object and discriminates its material whether it
is an animal or not. When all of the above mentioned switches are OFF, the
measurement of distance and the discrimination of material are not carried
out because Cancel Measure ("0") command is issued to the ECU 1.
When the head light is lit, the front object monitoring unit 10
automatically performs the measurement of distance and the discrimination
of material of the front object without requiring the driver to command
Front Monitoring. When it discriminates the front object as an "animal",
the buzzer on the control/display board 4 sounds continuously and
"Pedestrian, at xxx m Ahead" is displayed on the two-dimensional display.
While the invention has been particularly shown and described with
reference to preferred embodiments thereof, it will be understood by those
in the art that the foregoing and other changes in form and details may be
made therein without departing from the spirit and scope of the invention.
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